Adjustable electric buzzer

ABSTRACT

A ferromagnetic pole piece with a coil therearound is attached at one end to a ferromagnetic frame and a ferromagnetic armature is pivoted to the frame for vibratory movement toward and away from the other end of the pole piece to form a buzzer. The pivotal attachment of the armature includes non-magnetic pivot bearings which are so positioned as to direct the flow of magnetic flux between the frame and armature into a path which enters the armature transversely and thus eliminates undesirable vibration of the armature at the pivot bearings when the armature is pivoted on a conical end face of the pole piece in the &#39;&#39;&#39;&#39;off&#39;&#39;&#39;&#39; position. The intensity of the buzzing sound is controlled by a variable abutment member which varies the maximum air gap between the free end of the armature and the pole piece, which abutment member includes a rotatable shaft with a cam member positioned to vary the limit of movement of the armature away from the pole piece.

United States Patent [1 1 Primary Examiner1-larold Broome Att0rneyArthurL. Morsell, Jr.

Schantz etal. [45] J 8, 1974 ADJUSTABLE ELECTRIC BUZZER [57] ABSTRACT[75] Inventors: Spencer C. Schantz, 16608 W. A ferromagnetic pole piecewith a coil therearound is Rogers Dr., New Berlin, Wis. attached at oneend to a ferromagnetic frame and a 53151; William R. Berry,ferromagnetic armature is pivoted to the frame for vi- Menomonee Falls,Wis. bratory movement toward and away from the other 4 end of the polepiece to form a buzzer. The pivotal at- [73] Asslgnee: f schamz NewBerlm, tachment of the armature includes non-magnetic pivot bearingswhich are so positioned as to direct the flow [22] Fi d; June 21 1972 ofmagnetic flux between the frame and armature into a path which entersthe armature transversely and thus [21] Appl 264899 eliminatesundesirable vibration of the armature at the pivot bearings when thearmature is pivoted on a coni- [52 us. Cl. 335/276, 335/128 eel end faceof the p Pieee in the Position- 51 1nt.C1. 1101: 7/14 The intensity ofthe buzzing sound is controlled y a [58] Field of Search 335/276, 128variable abutment member which varies the maximum air gap between thefree end of the armature and the [56] References Ci d pole piece, whichabutment member includes a rotat- UNTED STATES ATENTS able shaft with acam member positioned to vary the limit of movement of the armature awayfrom the pole 2,471,181 5/1949 Wilson .1 335/276 piece. 2,398,657 4/1946McMaster et a1.... 335/276 2,884,574 4/1959 Jaidinger 335/276 9 Claims,7 Drawing Figures /0 L1 ni i l// //////Df 7" I 1 54 28 v I 25 I -54 I 1ADJUSTABLE ELECTRIC BUZZER BACKGROUND or THE INVENTION This inventionrelates to electromagnetic buzzers, relays, and other electromagneticdevices in which an armature is magnetically attracted to a pole piecewhen an alternating current is passed through a coil around the polepiece. Many such devices have been manufactured in the past, but allhave tended to vibrate and hum at the pivotal connection between thearmature and the frame thereof unless a means is provided to hold theparts together in intimate contact. This undesired vibration is causedby the alternating magnetic flux that traversed the pivotal connectionbetween the armature and frame at right angles to the armatureattracting said armature to the frame. In accordance with thisinvention, however, it has been found that such undesired vibration andhum can be eliminated by pivoting the armature on non-magnetic pivotbearings which are so positioned as to direct the flow of magnetic fluxbetween the frame and the armature into a path which enters the armaturetransversely and thus eliminates the undesired vibration.

Accordingly, one general object of this invention is to provide anelectromagnetic device in which undesired vibration of the armature atits pivot points is eliminated.

In its more particular aspects, this invention relates to improvementsin electric buzzers such as utilized in doorbells, interofficecommunication systems, and in various types of warning devices. Manydifferent types of buzzers have been manufactured in the past, butalthough these buzzers fulfilled their primary function as noiseemitters, they have suffered from shortcomings in terms of ease ofadjustment, adjustment stability, range of adjustment, reliability, andeconomy.

Accordingly, another object of this invention is to provide an improvedelectric buzzer.

An additional object of this invention is to provide an electric buzzerhaving a volume adjustment mechanism which can be easily varied fromzero sound output to a maximum sound output.

A further object of this invention is to provide an electric buzzerhaving a volume adjustment mechanism which can be adjusted in smallincrements from zero sound output to a maximum sound output.

Yet another object of this invention is to provide an electric buzzerhaving a volume adjustment mechanism which has improved stability.

A further object of this invention is to provide an electric buzzerhaving improved reliability.

A more specific object of this invention is to provide an electricbuzzer in which the armature is pivoted upon non-magnetic bearings, thebearings being so positioned as to direct the flow of magnetic flux intoa path which enters the armature transversely and thus eliminatesundesirable vibration of the armature adjacent to the pivot bearings,particularly when the unit is adjusted in the non-buzzing mode and whenthe armature is lifted from the hinge point by an adjusting cam.

A further, more specific object of the invention is to provide a buzzerin which an end face of the pole piece is conical to form a novelfulcrum for the armature when it is moved to the off position by theaction of an adjusting cam. This positively prevents buzzing and alsocompensates for manufacturing tolerances as it serves to lift the hingeend of the armature off of the non-magnetic bearings.

SUMMARY OF THE INVENTION In accordance with this invention, theabove-noted objects are attained by providing a ferromagnetic pole piecewhich is attached at one end to a ferromagnetic frame. An electric coilis positioned around the pole piece and a ferromagnetic armature ispivotally attached to the frame for vibratory movement toward and awayfrom the other end of the pole piece. The pivotal attachment of thearmature includes non-magnetic pivot bearings which are so positioned asto direct the flow of magnetic flux between the frame and the armatureinto a path which enters the armature transversely and thus eliminatesundesirable vibration of the armature at the pivot bearings. When thecoil is energized by alternating current, the free end of the armaturevibrates and produces a buzzing sound. The intensity of the buzzingsound is controlled by a variable abutment member which varies themaximum air gap between the free end of the armature and pole piece.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevational sectionalview of one illustrative embodiment of the invention;

FIG. 2 is a sectional view taken on the line 2-2 of FIG. 1;

FIG. 3 is a sectional view taken on the line 3--3 of FIG. 1;

FIG. 4 is a perspective view of the variable abutment member for theembodiment shown in FIGS. L3;

FIG. 5 is a perspective view of the coil bobbin for the embodiment shownin FIGS. 1-3;

FIG. 6 is a perspective view of an electric terminal for the embodimentshown in FIGS. l3; and

FIG. 7 is a fragmentary sectional view of the bobbin to show thecrushable ring which compensates for manufacturing tolerances.

DETAILED DESCRIPTION OF THE INVENTION Referring to FIG. ll, oneillustrative embodiment of the invention is enclosed in a housingconsisting of a top member 10 and a bottom cupmember 12 which may bemade of a suitable insulating plastic material. A U-shaped frame 14which is made of ferromagnetic material is suitably attached throughslotted engagement as at 16 and 18 to the top member 10 and projectsdownwardly into the cup member 12. A ferromagnetic core 20 forming apole piece is staked at its lower end to the bottom of the U-shapedframe 14 as at 15 (FIG. 1) and has an electric coil 22 positionedtherearound. The electric coil 22 is wound upon a nylon bobbin 24 whichhas a concentric hole 26 (FIG. 5) through which the pole piece 20passes. The pole piece 20 has an enlarged upper end face 28 which holdsthe bobbin 24 in position on the frame 14 and which is seated on aslightly crusted annular ring 23 around the core opening, as shown inFIG. 7, for a purpose to be hereinafter described.

A ferromagnetic armature 30 is pivoted on frame 14 in a novel manner onbearing pivots 32 (FIG. 1) for movement toward and away from the endface 28 of pole piece 20, there being a slot 27 in the armature throughwhich a reduced width portion 15 of the frame loosely passes. The pivotbearings are formed on the ends of legs 34 which project from oppositesides of the bobbin, as shown in FIG. 5. In order to provide support,these legs rest on shoulders 31 on each side of the reduced portion ofthe frame, as is shown in FIG. 2, and serve to rotationally position thebobbin. The armature 30 is normally urged away from the pole piece endface 28 by an extension spring 36, which also urges the armature 30toward the pivot bearings 32 and, being on an angle, urges armature 30against the frame in a transverse direction. The pivot bearings 32 aremade of a non-magnetic material and are so positioned with respect tothe U-shaped frame 14 and the armature 30 as to direct the magnetic fluxinto a path which enters the armature transversely and thus eliminatesundesirable vibration of the armature at its pivot points. In the past,the armature 30 was allowed to rest directly on shoulders on the frame14, and this allowed the magnetic flux at the pivot point to enter thearmature 30 in aperpendicular direction which caused undesirablevibration and hum when the magnetic flux alternated. Although the pivotbearings 32 can be made of any non-magnetic material, they arepreferably made of Nylon or some other suitable wear-resistant plasticand are preferably an integral part of the Nylon bobbin 24 as shown inFIG. 5. As an important feature of the invention the end face 28 of thepole piece is conical in form for a purpose to be hereinafter described.

The ends of electrical coil 22 are soldered to L- shaped electricalterminals 38 and 40 which are supported in pockets in a projection 42 onbobbin 24, as will be described in detail later, and project throughopenings in the bottom member 12 of the housing. When an alternating orpulsating current is applied between the terminals 38 and 40, analternating magnetic flux field is established in a magnetic circuitthat ex tends from the bottom of pole piece through frame 14 andarmature to the top 28 of pole piece 20. This causes the armature 30 tobe alternatingly attracted to pole piece end 28 and then released formovement away from end 28 under the impetus of spring 36 which producesa buzzing sound. The volume of this buzzing sound can be varied fromzero to a maximum value by a variable abutment member which will bedescribed in detail later.

The electric terminal elements 38 and 40 can be supported in anysuitable manner, but their bent upper portions are preferably supportedin pockets 44 and 46 (FIG. 5) in the projection 42 of bobbin 24. Thedownwardly-projecting portions of the terminals 38 and 40 (upwardly inFIG. 5) are surrounded by nylon barriers 45 which fit in notched-outside recesses 47 in the bottom portion of the metal frame 14. Thus thesenylon barriers serve to insulate the terminals from the frame 14 andalso aid in holding and positioning the bobbin on the frame. Protrusions48 and 50 from the plastic are formed in the interior of pockets 44 and46. Each terminal 38 or 40 has a hole 52 (FIG. 6) in the end which fitsinto its pocket. Each hole 52 is positioned beneath a plastic protrusion48 or 50 so that when the wires from coil 22 are soldered to theterminals, the heat will be conducted through the terminals to softenthe protrusions 48 and 50 and cause the nylon material to flow into theopenings 52 as shown in FIG. 3. This anchors the terminals 38 and 40securely in place in the pockets 44 and 46.

The volume of the sound produced by the buzzer can be varied in a novelmanner by means of an adjustable abutment member. The latter consists ofa shaft 54, a sector-shaped cam member 56 which projects laterally fromthe shaft 54, and a manually-operable extension 58 for the shaft 54. Theshaft is rotatably mounted parallel to pole piece 20 in openings intoplO and frame 14. The cam member 56 is interposed between the free endof armature 30 and the top 10. As best shown in FIGS. 3 and 4, the cammember 56 varies in thickness along its periphery so that when the shaftis rotated, the effective thickness of the cam member interposed betweenthe tip of armature 30 and top 10 is varied, the cam having an abruptchange of slope 31 leading to a portion of maximum thickness 33. Thisvaries the maximem air gap between the armature 30 and the pole pieceend 28 from zero to a maximum value and thus varies the volume ofbuzzing from zero to a maximum level. The shaft portion 58 is flattenedalong its length to fit into a manual adjustment knob which is not shownin the drawings.

The cam member 56 has serrations 60 formed on its upper surface whichengage a rib 62 that is pressed into the top 10 and projects downwardlya short distance therefrom. A spring 64 urges the cam member 56 towardthe top 10 and resiliently holds the serrations 60 in contact with rib62 to produce a ratchet effect with a pleasing feel when the shaft 58 isrotated. This holds the cam member 56 in position after it has beenadjusted in spite of the vibration of the armature 30.

The cam member 56 is, in its peripheral dimension, shaped like a sectorof a ring and the radial edges of cam member 56 abut against theferromagnetic frame 14 when the shaft 58 is turned to extreme position.One extreme position is where the thinnest portion of cam member 56 isinterposed between armature 30 and top 10. This is the position shown inFIGS. 1-3, and in this position, the thickest portion 66 (FIG. 4) of cammember 56 abuts against the frame 14 to limit rotation. The otherextreme position is where the thickest portion 66 of cam member 56 isinterposed between armature 30 and top 10. In this position, thethinnest portion of cam member 56 abuts against the frame 14.

By having the end face 28 of the pole piece conically shaped as shown inFIG. 1 it is possible, when te adjustment cam is rotated to bring itsthickest portion 66 into effective engagement with the end of thearmature, to cause the armature to rock on an intermediate fulcrumprovided by the top of the conical end face 28 whereby the left hand endof the armature is lifted off of the pivots 32. This positively preventsbuzzing action and also compensates for manufacturing tolerances.

It is to be noted that the spring 36 extends obliquely between the endof the armature and the frame thereby tending to pull the margin of thearmature slot into metal-to-metal contact with the frame portion 15 tocomplete the magnetic circuit.

The crushable or yielding annular ring 23 which projects upwardly fromthe bobbin around the core opening (as shown in FIG. 7) is integrallymolded with the bobbin. During assembly, after the core 20 has beeninserted through the bobbin, its lower end is staked to the underside ofthe base of the frame 14, as is common practice and as shown at 15 inFIG. 1. During such staking, however, there is a controllable slightreduction of the height of the core to compensate for manufacturingtolerances and this may vary slightly from one lot of parts to another.The ring 23, being made of yieldable or crushable plastic material suchas Nylon, will yield or be in a condition of having been controllablyreduced in height a required amount, as the core is being staked inplace, to allow for such manufacturing tolerances. At the same time,because of the presence of the ring, the bobbin is always kept tightagainst axial movement relative to the core. This is an importantfeature as it insures accurate assembly and eliminates the necessity ofusing a spring washer to absorb tolerances.

From the foregoing description it will be clear that this inventionprovides an improved electric I buzzer. And although this invention hasbeen described with reference to one specific embodiment thereof, itshould be understood that the invention is not limited to the disclosedembodiment since many modifications can be made in the disclosedstructure without changing its essential principles. For example,although the armature pivot bearings have been disclosed as beingattached to the coil bobbin, they could be otherwise supported ifdesired. This and many other modifications of the disclosed structurewill be apparent to those skilled in the art, and this inventionincludes all modifications falling within the scope of the followingclaims.

What is claimed is:

1. An electromagnetic device comprising a ferromagnetic frame, aferromagnetic pole piece attached at one end to said frame, an electriccoil on said pole piece, a ferromagnetic armature loosely pivoted tosaid frame for vibratory movement toward and away from the other end ofsaid pole piece, spring means attached between said armature and saidframe in such position as to normally urge part of said armature againstsaid loose pivot and another part away from the end of said pole piece,and said pivot including at least one wear resistant pivot bearingintegrally molded with bobbin.

2. An electromagnetic device comprising a magnetic frame, a magneticpole piece attached at one end to said frame, an electric coil on saidpole piece, a magnetic armature loosely pivoted to said frame forvibratory movement toward and away from the other end of said polepiece, spring means attached between said armature and said frame insuch position as to normally urge part of said armature against saidloose pivot and another part away from the end of said pole piece, andsaid pivot including at least one nonmagnetic pivot bearing sopositioned between said armature and said frame as to direct the flow ofmagnetic flux between said frame and said armature into a path whichenters the armature transversely and thus eliminates undesirablevibration of said armature on its loose pivot, said electric coil beingwound upon a bobbin made of nonmagnetic material, and said non-magneticpivot bearing being integrally joined to one end of said bobbin andprojecting laterally therefrom.

3. An electromagnetic device as defined in claim 2 wherein said framehas a side portion spaced laterally from the pole piece and extending inthe same general direction, said side portion having spaced shoulders,and whereinthere are spaced arms projecting from the bobbin on whichsaid pivot bearings are formed, said arms being supported on the spacedshoulders of said frame and serving to locate and support the adjacentend of the bobbin.

4. An electromagnetic device as defined in claim 3 in which said frameside portion has an upper end of re duced width to provide said spacedshoulders and wherein said armature has a transverse slot through whichsaid portion of reduced width loosely extends.

5. An electromagnetic device such as defined in claim 3 in which saidpivot bearing is located at one end of said non-magnetic bobbin, andfurther comprising pockets formed in the other end of said bobbin, andelectric terminals having portions secured in said pockets.

6. An electromagnetic device such as defined in claim 5 in which saidbobbin is made of a thermoplastic material, andin which there is aprotrusion in each of said pockets and an opening in each of saidelectric terminals, said protrusions being positioned to overlie saidopenings in said electric terminals with portions thereof in heat-flowinterlocking relationship therewith.

7. An electromagnetic device comprising a magnetic frame, a magneticpole piece attached at one end to said frame, an electric coil in saidpole piece, a magnetic armature loosely pivoted to said frame forvibratory movement toward and away from the other end of said polepiece, spring means attached between said armature and said frame insuch position as to normally urge part of said armature against saidloose pivot and another part away from the end of said pole piece, andsaid pivot including at least one non-magnetic pivot bearing sopositioned between said armature and said frame as to direct the flow ofmagnetic flux between said frame and said armature into paths which areparallel to the plane of the armature, the non-magnetic pivot bearingbeing positioned to block flow of the magnetic flux in a direction whichwould effect seating of the armature on said pivot bearing, thuseliminating undesirable vibration of said armature on its loose pivot.

8. An electromagnetic device comprising a magnetic frame, a magneticpole piece attached at a first end to said frame, an electric coil forsaid pole piece, a magnetic armature, pivot means on said frame on whichsaid armature is loosely pivoted forvibratory movement toward and awayfrom the other end of said pole piece, spring means attached betweensaid armature and frame in such a position as to normally urge part ofsaid armature against said loose pivot means and another part away fromthe end of said pole piece, a bobbin on which said electric coil iswound, spaced arms projecting from said bobbin and having said pivotmeans thereon, said frame having a side portion spaced laterally fromthe pole piece and extending in the same general direction, and saidside portion having spaced shoulders, said spaced arms which projectfrom the bobbin being supported on said spaced shoulders of said frameand serving to locate and support the adjacent end of the bobbin.

9. An electromagnetic device comprising a magnetic frame, a magneticpole piece attached at a first end to said frame, an electric coil forsaid pole piece, a magnetic armature, pivot means on said frame on whichsaid armature is loosely pivoted for vibratory movement toward and awayfrom the other end of said pole piece, spring means attached betweensaid armature and frame in such a position as to normally urge part ofsaid armature against said loose pivot and another part away from theend of said pole piece, a bobbin on which said electric coil is wound,said bobbin being made of thermoplastic material and having pocketsformed in its end which is remote from the armature, electric terminalshaving portions secured in said pockets, there being a protrusion ineach of said pockets and an opening in each of said electric terminals,said protrusions being positioned to overlie said openings in saidelectric terminals with portions thereof in heatflow interlockingrelationship therewith.

1. An electromagnetic device comprising a ferromagnetic frame, aferromagnetic pole piece attached at one end to said frame, an electriccoil on said pole piece, a ferromagnetic armature loosely pivoted tosaid frame for vibratory movement toward and away from the other end ofsaid pole piece, spring means attached between said armature and saidframe in such position as to normally urge part of said armature againstsaid loose pivot and another part away from the end of said pole piece,and said pivot including at least one wear-resistant pivot bearingintegrally molded with bobbin.
 2. An electromagnetic device comprising amagnetic frame, a magnetic pole piece attached at one end to said frame,an electric coil on said pole piece, a magnetic armature loosely pivotedto said frame for vibratory movement toward and away from the other endof said pole piece, spring means attached between said armature and saidframe in such position as to normally urge part of said armature againstsaid loose pivot and another part away from the end of said pole piece,and said pivot including at least one non-magnetic pivot bearing sopositioned between said armature and said frame as to direct the flow ofmagnetic flux between said frame and said armature into a path whichenters the armature transversely and thus eliminates undesirablevibration of said armature on its loose pivot, said electric coil beingwound upon a bobbin made of non-magnetic material, and said non-magneticpivot bearing being integrally joined to one end of said bobbin andprojecting laterally therefrom.
 3. An electromagnetic device as definedin claim 2 wherein said frame has a side portion spaced laterally fromthe pole piece and extending in the same general direction, said sideportion having spaced shoulders, and wherein there are spaced armsprojecting from the bobbin on which said pivot bearings are formed, saidarms being supported on the spaced shoulders of said frame and servingto locate and support the adjacent end of the bobbin.
 4. Anelectromagnetic device as defined in claim 3 in which said frame sideportion has an upper end of reduced width to provide said spacedshoulders and wherein said armature has a transverse slot through whichsaid portion of reduced width loosely extends.
 5. An electromagneticdevice such as defined in claim 3 in which said pivot bearing is locatedat one end of said non-magnetic bobbin, and further comprising pocketsformed in the other end of said bobbin, and electric terminals havingportions secured in said pockets.
 6. An electromagnetic device such asdefined in claim 5 in which said bobbin is made of a thermoplasticmaterial, and in which there is a protrusion in each of said pockets andan opening in each of said electric terminals, said protrusions beingpositioned to overlie said openings in said electric terminals withportions thereof in heat-flow interlocking relationship therewith.
 7. Anelectromagnetic device comprising a magnetic frame, a magnetic polepiece attached at one end to said frame, an electric coil in said polepiece, a magnetic armature loosely pivoted to said frame for vibratorymovement toward and away from the other end of said pole piece, springmeans attached between said armature and said frame in such position asto normally urge part of said armature against said loose pivot andanother part away from the end of said pole piece, and said pivotincluding at least one non-magnetic pivot bearing so positioned betweensaid armature and said frame as to direct the flow of magnetic fluxbetween said frame and said armature into paths which are parallel tothe plane of the armature, the non-magnetic pivot bearing beingpositioned to block flow of the magnetic flux in a direction which wouldeffect seating of the armature on said pivot bearing, thus eliminatingundesirable vibration of said armature on its loose pivot.
 8. Anelectromagnetic device comprising a magnetic frame, a magnetic polepiece attached at a first end to said frame, an electric coil for saidpole piece, a magnetic armature, pivot means on said frame on which saidarmature is loosely pivoted for vibratory movement toward and away fromthe other end of said pole piece, spring means attached between saidarmature and frame in such a position as to normally urge part of saidarmature against said loose pivot means and another part away from theend of said pole piece, a bobbin on which said electric coil is wound,spaced arms projecting from said bobbin and having said pivot meansthereon, said frame having a side portion spaced laterally from the polepiece and extending in the same general direction, and said side portionhaving spaced shoulders, said spaced arms which project from the bobbinbeing supported on said spaced shoulders of said frame and serving tolocate and support the adjacent end of the bobbin.
 9. An electromagneticdevice comprising a magnetic frame, a magnetic pole piece attached at afirst end to said frame, an electric coil for said pole piece, amagnetic armature, pivot means on said frame on which said armature isloosely pivoted for vibratory movement toward and away from the otherend of said pole piece, spring means attached between said armature andframe in such a position as to normally urge part of said armatureagainst said loose pivot and another part away from the end of said polepiece, a bobbin on which said electric coil is wound, said bobbin beingmade of thermoplastic material and having pockets formed in its endwhich is remote from the armature, electric terminals having portionssecured in said pockets, there being a protrusion in each of saidpockets and an opening in each of said electric terminals, saidprotrusions being positioned to overlie said openings in said electricterminals with portions thereof in heat-flow interlocking relationshiptherewith.